feat(tvix/eval): implement correct toString behavior r/4857

Implement C++ Nix's `EvalState::coerceToString` minus some of the Path
/ store handling. This is currently only used for `toString` which does
all possible coercions, but we've already prepared the weaker coercion
variant which is e.g. used for builtins that expect string arguments.

`EvalState::coerceToPath` is still missing for builtins that need a
path, but it'll be easy to build on top of this.

Change-Id: I78d15576b18921791d04b6b1e964b951fdef22c6
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6571
Autosubmit: sterni <sternenseemann@systemli.org>
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI

1 files changed, 3 insertions, 3 deletions

diff --git a/tvix/eval/src/vm.rs b/tvix/eval/src/vm.rs
index d886bf24b9..6fe94184b8 100644
--- a/tvix/eval/src/vm.rs
+++ b/tvix/eval/src/vm.rs
@@ -148,11 +148,11 @@ impl<'o> VM<'o> {
         op
     }
 
-    fn pop(&mut self) -> Value {
+    pub fn pop(&mut self) -> Value {
         self.stack.pop().expect("runtime stack empty")
     }
 
-    fn push(&mut self, value: Value) {
+    pub fn push(&mut self, value: Value) {
         self.stack.push(value)
     }
 
@@ -726,7 +726,7 @@ impl<'o> VM<'o> {
         }
     }
 
-    fn call_builtin(&mut self, builtin: Builtin) -> EvalResult<()> {
+    pub fn call_builtin(&mut self, builtin: Builtin) -> EvalResult<()> {
         let builtin_name = builtin.name();
         self.observer.observe_enter_builtin(builtin_name);